What is the purpose of sandblasting treatment for 201 stainless steel welding pipes

201 The main purpose of sandblasting treatment for stainless steel welded pipes is to achieve surface cleaning, strengthening, and roughening effects by subjecting the pipe surface to high-speed impact from abrasive materials (such as quartz sand, steel shot, glass beads, etc.). The specific functions and application scenarios are as follows: 

I. Core Objective Analysis

1. Removal of Surface Impurities and Oxide Layers

Post-welding treatment: After welding, the surface of the welded pipe often contains oxide scales, welding slag, and splatter, etc. Sandblasting can thoroughly remove these impurities, exposing the fresh metal surface, and preparing for subsequent coating or passivation.

Example: After welding of 201 pipe, the oxide layer on the surface will reduce the corrosion resistance. Sandblasting can remove the oxide layer and activate the surface, enhancing the formation effect of the passivation film. 

2. Improve surface roughness and enhance adhesion

Coating substrate treatment: Sandblasting creates a uniform microscopic rough structure on the surface (with a roughness Ra value ranging from 50 to 100 μm), significantly increasing the contact area between the coating (such as paint, powder coating) and the pipe, enhancing adhesion and preventing coating detachment.

Application scenarios: When used for outdoor decorative pipes (such as railings, curtain walls), spraying paint after sandblasting can extend the coating lifespan by 3 to 5 times. 

3. Eliminate stress and enhance fatigue strength

Shot peening: Using hard abrasive materials such as steel balls for sandblasting (also known as "shot peening"), a compressive stress layer can be generated on the surface, counteracting the tensile stress caused during welding or processing, reducing the risk of cracks due to stress concentration, especially suitable for structural components subjected to vibration or impact loads.

Reference data: The fatigue life of 201 welded pipes after shot peening can be increased by 20% to 50%. 

4. Beautify appearance, unify texture

Matte finish: Sandblasting can give the pipe surface a uniform matte texture, covering scratches, welds and other defects, enhancing the aesthetic appeal. It is commonly used in decorative fields (such as architectural decoration, furniture).

Color adjustment: Different abrasives (such as quartz sand, glass beads) can produce different surface tones (such as grayish white, silver gray), meeting diverse design requirements. 

5. Special Pre-treatment Processes

Pre-treatment for coating: As the pre-process for spraying, galvanizing, electrophoretic coating, etc., sandblasting can ensure the cleanliness of the substrate and the appropriate roughness, thereby enhancing the corrosion resistance and durability of the subsequent coatings.

Composite treatment: When combined with the passivation process, sandblasting can remove surface impurities, allowing the passivation solution to more evenly contact the metal surface and form a dense passivation film. 

II. Compatibility of Sandblasting with the Properties of 201 Stainless Steel

1. Leveraging Strengths and Avoiding Weaknesses

The corrosion resistance of 201 stainless steel is relatively weak. After sandblasting, it is necessary to promptly apply coating or passivation treatment to seal the surface pores and prevent corrosive media from penetrating.

Sandblasting can improve the microscopic defects (such as tiny cracks) on the surface of 201, but it cannot make up for the inherent insufficient corrosion resistance caused by its composition. Therefore, other protective measures (such as coatings) still need to be combined. 

2. Process Risk Control

Iron contamination risk: If using ordinary steel sand for sandblasting, iron particles may remain on the surface of the pipe, accelerating rusting. It is necessary to use stainless steel sand or glass beads and conduct thorough cleaning after the sandblasting.

Surface hardening: Excessive sandblasting may cause surface hardening (an increase in hardness of 20%-30%), reducing the toughness of the pipe. The sandblasting pressure and time need to be controlled. 

III. Typical Application Scenarios

Outdoor railings and handrails

Sandblasting purpose: Remove oxide layer + Achieve matte finish + Prepare coating base

Supporting process: After sandblasting, apply fluorocarbon paint or powder coating 

Chemical equipment support

Sandblasting purpose: Remove impurities + Enhance coating adhesion

Supporting process: Sandblasting → Hot-dip galvanizing → Epoxy zinc-rich primer 

Car exhaust pipe

Sandblasting purpose: Eliminate welding stress + Improve coating adhesion

Supporting process: Shot peening treatment → High-temperature resistant coating 

Building decoration components

Purpose of sandblasting: To achieve uniform appearance texture and cover defects

Matching process: After sandblasting, electrochemical coloring or chemical passivation is carried out 

IV. Impact of Process Parameters on Results

Grinding Material Type

Function: Determines the roughness and surface hardness

Recommended Range (for 201 Stainless Steel): Glass beads (fine matte finish), Stainless steel sand (reinforced) 

Sandblasting pressure

Function: Affects roughness and processing efficiency

Recommended range (for 201 stainless steel): 0.4 - 0.6 MPa (Avoiding too high pressure which may cause surface brittleness) 

Spray distance

Function: Controls the impact intensity of the abrasive

Recommended range (201 stainless steel): 100 - 150mm 

Angle

Function: Affects surface uniformity

Recommended range (201 stainless steel): Mainly vertical spraying (90°), with consideration for multiple angles 

Summary

201 stainless steel welded pipe sandblasting treatment is a multi-functional surface modification technology. It mainly enhances the performance of the pipe by cleaning, roughening and strengthening processes. It is particularly suitable for scenarios where there are requirements for appearance, coating adhesion or fatigue strength. However, it should be noted that sandblasting cannot alter the inherent corrosion resistance of 201 stainless steel. In high-corrosive environments, other protective measures (such as passivation and coating) need to be used in conjunction.